Complications of Growing Up Twice
by Alshoruzen
Summary: To his dismay, Shinichi's found that leaving his Conan days behind has come with a problem. He's sure it's a side effect of the antidote, but it's really just a side effect of growing up. Luckily, a certain thief is all too eager to help. KaiShin


Disclaimer: I do not own Detective Conan/Case Closed.

Pairing: Established KaitoxShinichi

Rating: M

Genre: Romance

 **Warning: Lots of smut, you have been warned!**

Summary: To his dismay, Shinichi's found that leaving his Conan days behind has come with a problem. He's sure it's a side effect of the antidote, but it's really just a side effect of growing up. Luckily, a certain thief is all too eager to help.

* * *

 **Complications of Growing Up Twice**

The air in the room was thick and heavy with heat. But it wasn't a suffocating atmosphere. No, not at all.

Hearts raced. The silence was broken only by soft gasps and stifled moans. However, as the two figures on the room's one bed continued their heated dance, those stifled moans were gradually growing louder. Every now and then, they would be interrupted by a sharp cry.

Like now.

Shinichi tossed his head back with a cry as his lover hit that spot again ( _and again and again and again_ ), sending sparks of pleasure dancing along his nerves. In that instant, he had inadvertently exposed his neck to his lover, and Kaito was all too ready to take advantage of the fact to bite and lick at pale, sensitive skin, leaving his mark.

To Shinichi, it seemed as though the whole of his awareness had become a broiling cauldron of sensation in which no coherent thoughts could form. All of his senses—all of his being—was filled only with Kaito and the overwhelming pleasure being inflicted upon him—drowning and consuming him—as his thief's hot body moved against and inside him.

He couldn't help but moan Kaito's name each time the magician thrust into him. Only he wasn't moaning now so much as he was crying out—sharp, breathless cries that only spurred his lover on. His thief's thrusts became harder, wilder—deeper—

Shinichi writhed, fighting to hang on, not wanting the incredible pleasure of their dance to end just yet. But the stimulation was simply too much. He came hard, back arching as his inner muscles clenched tight around the hard cock still thrusting inside him.

Kaito followed soon after, spilling his hot seed deep inside his lover's body.

Shinichi half moaned, half whimpered at the sensation. Every nerve in his body was still tingling with heat and pleasure.

Blinking open eyes he hadn't meant to close, he met a pair of indigo eyes. They were full of warmth and love, and he couldn't help but smile softly back. Kaito leaned down and placed a soft kiss on his lips before shifting to pull gently out of his detective. Then he lay down beside Shinichi and pulled him close.

Shinichi let out an almost inaudible sigh at the sudden emptiness. It was a feeling of loss. He was half tempted to see if Kaito wanted to continue, but it had been a long day, it was late, and they'd already had quite the _eventful_ night. Frankly he was too tired to move. It was just…

He liked being filled by Kaito.

He blushed, burying his face in the pillow, trying not to think about the warm, solid body pressed against his back or the strong arm wrapped around his waist but acutely aware of both despite his efforts.

It was a while before he was able to drift off to sleep.

-0-

He was sure it was a side effect of the antidote. It seemed his body wasn't just readjusting to having longer limbs but all those hormones coming back too. Everything felt just a little oversensitive. It was puberty all over again, except it was worse this time because it was happening all at once instead of gradually as nature had intended.

Ai had rolled her eyes and scoffed when he went to her about it. "I can't give you something to fix it. It's not an illness, it's just nature. Your body will adjust on its own, you just have to give it time. Everyone does it. It's part of growing up. So suck it up and don't bother me about it again."

So basically Haibara had been no help. Although he supposed it helped a tiny, tiny little bit to know that it wasn't some kind of _real_ problem. That didn't make it any less annoying (and embarrassing). So it seemed one nice thing about being a child again had been NOT having any teenage hormones to deal with.

He swore that growing up had not been this bad the first time around. Then again, the first time around he'd been focused on beginning his lifelong dream of becoming a detective. His days had pretty much been consumed by thoughts of mysteries, crime solving, and the path to acquiring the knowledge and deductive skills he would need. Everything else had been of a lesser priority. Besides, he'd been young and naïve and everything else that _that_ came with.

This time around, he was much more aware in all senses of the word. His life had also settled down a great deal—as much as his life ever could anyway. Though he was still in university, his career was basically set. School itself was interesting, but the class work didn't take him much time. There were cases, but it seemed things were calming down on that front too for the time being. Which was good. It was nice to know that fewer people were trying to get rid of their problems by killing each other off instead of actually putting their brains to proper use and solving them. But it also meant that he actually had free time these days. Something he hadn't actually expected in the hurricane of activity that had come with the takedown of the Black Org and finally getting an antidote.

And of course he couldn't forget the biggest change in his life.

Kaito.

Before, he would never in a million years have thought that he would end up falling in love with a criminal—let alone _the_ infamous Kaitou KID. But though he'd struggled with the idea for a while, he couldn't regret it. Kaito was…

 _(Amazing, brilliant—absolutely insane)_

Kaito was someone he could depend on. A close friend he trusted with all his secrets and someone he was comfortable sharing all his burdens with. He was an equal Shinichi could rely on to watch his back and one of the only people that Shinichi felt really understood him. Perhaps because they had weathered many of the same storms and upheld—if not the same—similar beliefs and codes of honor.

So yeah, having Kaito in his life was a change for the better. The magician was one of the reasons he no longer felt like following Gin and Vodka that day at Tropical Land had been the worst mistake of his life. The other reasons being that, looking back, he knew he had learned a lot from his experience as Conan, and he might even venture to say that he had become a better person because of it. But that was a different matter.

"Kudo-kun? Kudo-kun! Are you okay?"

Starting in surprise, Shinichi glanced around to see Takagi-keiji giving him a concerned look. "Oh, uh, sorry. What was that?"

"I was just asking if you agreed that this was an unplanned robbery."

"Oh, right. Yes, it seems that way. Have any of the officers found any witnesses yet?"

"We're still asking around. Are you sure you're okay? You seem…distracted."

"It's nothing," Shinichi assured him. It wasn't really a lie either. There wasn't technically anything wrong. It was just that the robbery they were currently investigating had occurred in a hat shop of all places. They had all sorts of hats in every color you could possibly imagine. That included top hats.

It was the sight of the display of white and black top hats that had caused Shinichi's momentary lapse of attention. After all, top hats were quite naturally associated with magicians. And he couldn't help but think of a certain thief whenever he thought about magicians. It hadn't helped that that white top hat at the end of the row there had a blue ribbon tied around it, making it look almost just like Kaito's KID hat. If the shade of blue was just a bit darker, it would be an exact replica.

In his mind's eye, he could see a gloved hand pulling the white brim down over indigo eyes as a wicked, white grin cracked the shadows. The sight of that grin always sent a thrill through Shinichi, whether it was at a heist as the thief challenged him to push his own physical and intellectual limits—

—or in the bedroom when Kaito leaned over him, sweat glistening on lightly tanned skin.

Shinichi hurriedly cut himself off before he could travel any farther down that train of thought. And damn, but he had done it again, hadn't he? Getting distracted. This was a crime scene for goodness sake! He should know better than to let his mind wander even if the suspects weren't currently on the scene and no one had died.

That's right. Shinichi gave himself a hard shake. It was time to focus!

-0-

Shinichi didn't usually mind writing essays. Writing was something he was good at, and making logical connections between ideas was second nature for a detective. The fact that the topic today was history rather than a crime didn't change much.

Today, however, he found that he was having difficulty concentrating. He had been sitting here for almost half an hour and written a total of one sentence. He groaned and slumped back in his seat.

He just wasn't in the mood for working on the essay right now. It wasn't due until the week after next anyway. Maybe he could just call it a day on the homework and read a book?

As he thought, his eyes landed on the tall, glass vase on the corner of the desk. It had a single red rose standing in it. A soft smile made its way onto his face. That was the vase where he had placed the very first rose Kaito had given him after he'd returned to being Shinichi again. Of course that particular rose had long since wilted, but Kaito made sure that the vase was never empty.

The magician had given him this particular bloom only five days ago (that passion-filled night was still vivid in his memories).

They had both had late exams that day. With his thoughts still buzzing with test questions, Shinichi had wound up in his library when he got home. He had been standing before this very desk, trying to decide whether to read a novel or check the answers to some of the more difficult questions he remembered from the test, when Kaito had surprised him by hugging him from behind.

 _"Kai!" he gasped, turning around in the loose embrace to see a familiar, grinning face. "I didn't hear the door."_

 _"That would be because I didn't use the door," the thief replied with a smug smirk. "Your house sure has a lot of big windows."_

 _Shinichi rolled his eyes. "Why did you ask me for a key if you're never going to use it?"_

 _Kaito only chuckled, leaning his forehead against Shinichi's. "That's different. Giving someone a key is a sign of trust. It doesn't mean the recipient has to use it."_

 _"…But it's a key. The whole point of giving someone a key is so they'll use it."_

 _"We'll just have to agree to disagree then."_

 _Shinichi found himself laughing a little at that. "I guess we will." On a whim, he leaned up and brushed a chaste kiss across the magician's lips. "I'm glad you came. I wasn't sure you would, since we both had exams."_

 _Kaito grinned. "All the more reason to come, I say." Unwinding one arm from around Shinichi, the magician flicked his wrist and produced a perfect, crimson rose. "We deserve a reward after all that hard work. Wouldn't you agree?"_

 _Shinichi murmured an absent agreement as he accepted the rose, reaching over to slip it into the glass vase on the corner of the desk. He had removed the previous occupant just that morning. It was amazing how Kaito always seemed to know. "What did you have in mind?"_

 _"Well, a nice dinner is a definite. As for after that…" Leaning in, Kaito pressed his lips against Shinichi's once again. The kiss was gentle but firm. Shinichi's eyes fluttered shut as he wrapped his arms around Kaito's neck and kissed back. The magician's hands slid to rest on his hips, lifting him slightly and pushing him backward._

 _Now Shinichi was sitting on the edge of the desk with his knees on either side of Kaito's hips._

 _"I thought you wanted to have dinner first," Shinichi said, though he made no move to push Kaito away._

 _Kaito smirked. "I think we can change up the schedule a bit."_

 _Shinichi might have commented, but he found his mouth otherwise occupied. Not that he was complaining._

Quite some time had passed before they got around to dinner. But they hadn't so much changed up the "schedule" as extended it.

Shinichi found himself remembering how it felt to have Kaito's strong arms wrapped around him, holding him close. Those thoughts led to others. Like how it felt when Kaito pinned him down on the bed as those devious hands stripped him bare. Shinichi blushed, beginning to feel hot. The memory of Kaito pounding into him made him shudder. He was mortified to realize that he was getting aroused just thinking about it, but he couldn't seem to _stop_ thinking about it.

This was a new problem for him. He never used to think much about these things at all. He wished the thoughts and feelings would just leave him alone.

…

He wanted to feel Kaito's touch again.

He groaned. This was all just so embarrassing.

He really hoped all of this went away soon so he could go back to being normal. His life was complicated enough without it.

Blue eyes turned to the book he'd originally been thinking about reading. It was still waiting for him on the shelf. He stood up from his seat at the desk and stepped towards it then stopped. He was still feeling hot from his unintentional trip down memory lane. He felt like his nerves were all a jangle.

Making up his mind, he pivoted and headed out of the library. What he really needed right now was a shower. Maybe that would clear his head. Then he could read in peace.

Hopefully.

-0-

The spray of the shower fell all around him. There was nothing quite like a shower to soothe away tension and relax the body.

He closed his eyes, imagining that it was Kaito's hands caressing his skin. The magician's hands were slightly bigger than his own and calloused from working with all those mechanisms, gadgets, and tools he employed for his magic. But if Shinichi tried, he could just about pretend.

He groaned when he realized what he was doing. He really was fighting a losing battle here, wasn't he? Well, if he couldn't get these thoughts out of his head…maybe if he just indulged a little bit. It wasn't like anyone would ever know. The house was empty, and he had already given up on getting any work done for the rest of today.

Without conscious direction from him, his hands wandered lower until they found their way to his half hard member. He swallowed a quiet moan as he imagined that it was Kaito touching him.

While he continued to stroke himself with one hand, he reached for the soap with the other. Covering his fingers in a thick coating of the slippery substance, he reached back. He hesitated for a moment before pushing a finger into himself. Part of him couldn't quite believe he was doing this, but the rest of him was lost in his mental fantasy where the hands touching him belonged to a certain phantom thief. He pushed the finger in and out a few times before adding a second finger. Quiet gasps fell unchecked from his lips as he continued to finger himself, imagining that it was Kaito touching him. His other hand continued its stroking as well. He could feel the tension building, but despite the pleasure he still couldn't quite find the feeling he was looking for.

"So this is what you get up to in here," a familiar voice said teasingly. "Shame on you. You should have invited me."

Shinichi froze, eyes flying open as he flushed beet red. "K—Kaito!"

"Oh no, don't stop on my account," said the grinning intruder standing behind him, having just shut the shower door. "Here, let me remind you where you were."

A larger, more calloused hand joined Shinichi's own (which had quite forgotten what it had been doing in the midst of his mortification) around his arousal. It teased at the tip before giving a firm pull that had Shinichi's knees going weak. Kaito's other hand joined Shinichi's fingers at the detective's entrance where a single long digit eased in alongside Shinichi's fingers, guiding them in the right direction as the hand pressed against Shinichi's, pushing them all deeper.

Shinichi's back arched as he moaned loudly. His body wanted both to move into those firm strokes on his member and to rock back onto those fingers pressing inside him.

Kaito smirked. "Now that's more like it. A good show gets the audience involved, hmm?"

Leaning back against his assailant's firm chest, Shinichi mustered a scowl. "You shouldn't invite yourself into locked bathrooms."

"But you're glad I did," Kaito pointed out, allowing Shinichi's hand to retreat before he added another finger and began to scissor them against that deliciously tight passage. The gesture elicited yet another series of gasping moans. He licked his lips. "Do you really want me to leave?"

Adding a third finger, he thrust in deeper and crooked his fingers, pressing and rubbing mercilessly at the spot he knew made his Shin-chan scream in pleasure.

Shinichi tossed his head back with a cry, hips rocking instinctively in response.

"I thought not."

Shinichi managed a glare, though there wasn't much heat to it (or rather none of that kind of heat. The other kind was quite a different story. God those fingers were working magic in there). "That's not fair. It's duress!"

"You can't really call it that," the magician purred low and seductive into his ear, "when we both know you _want_ it." His fingers crooked, pressing hard into that spot again with his words and Shinichi mewled. "Why don't you just admit it?"

Shinichi groaned.

He wanted it. He wanted it hard and fast, and he wanted it _now_ —

The words tumbled past his lips before he could stop them.

"What was that?"

" _I want you inside me_."

Kaito smirked. "That's a good boy."

Shinichi considered stepping on the stupid manipulative thief's foot, but he didn't because those teasing fingers were pulling out and being replaced by something bigger.

A long, breathless moan of pleasure escaped his mouth at the sudden strain in his bottom. Muscles flexed and stuttered.

Kaito let out a slightly breathy laugh against the side of his neck. "You really do have a naughty little ass, don't you?"

Shinichi had thought he couldn't possibly get any redder. He'd been wrong. "Sh—shut up," he gasped, cheeks burning. "Ah! You're such a pervert!" His mortification didn't stop him from pushing himself back and canting his hips to take the magician's hard cock in just a little bit deeper. His eyelids fluttered and his lips parted slightly in pleasure.

The strong arms around his middle tightened, and Kaito turned to press an open-mouthed kiss against the junction between Shinichi's neck and shoulder. He dragged his tongue across the detective's pale, heated skin then bit down. Shinichi's breath hitched in a strangled groan. Kaito was all but purring, savoring the sheer pleasure of being inside his detective's hot, tight passage. He could never have enough of this sensation (it was all the sweeter for the knowledge that Shinichi wanted him just as much as he wanted Shinichi—that his detective loved him enough to let him do this to him, and, indeed, found it as immensely pleasurable as Kaito did. It was, he thought, proof that Shinichi was truly his. Not that he really needed proof. He could see it in Shinichi's eyes and his smile).

"You're just so beautiful that I can't help but want to ravish you," he murmured, nibbling at the quivering skin beneath his lips and smirking when it reddened. "But you know, you were the one who was playing without me. Is it wrong of me to want to play with my Shin-chan?"

Shinichi flushed even redder at the reminder of just what he'd been caught doing earlier. "Just shut up and move al—ah!" He moaned as Kaito thrust into him, slow and deep.

He pressed his forehead against his arm where it was braced against the wet tiles. His other hand had found the railing on the door and closed in a vice grip.

Then Kaito was pulling out and thrusting back in again. Shinichi really was holding onto the walls to keep himself from falling now. His knees had gone weak with pleasure. Again and again, Kaito's hard length filled him. The pleasure of his thief's touch melted what was left of Shinichi's thoughts and all he wanted, all he could think about, was Kaito,. Kaito, Kaito…

When he came, he did so screaming Kaito's name.

-0-

"Now I need a shower to clean up from my shower," Shinichi grumbled.

"I'll help."

Shinichi snorted. "Any more help from you and we'll be here all day."

"I didn't hear you complaining. In fact, if you'll recall, it was quite the contrary." Then, just to illustrate his point, he said in a perfect imitation of Shinichi's voice. " _More, Kai, d—don't stop—!_ "

Turning bright red, Shinichi smacked him upside the head. "Just—just hurry and clean up so we don't waste any more water."

To Shinichi's relief (though a traitorous part of him was secretly disappointed), they made it out of the shower without encore number four.

They wound up in the kitchen where Shinichi immediately set about making coffee. He offered Kaito a mug, but the magician waved it away. Shrugging, Shinichi turned to lean his back against the counter as he sipped at the hot beverage.

"So do you often play with yourself in the shower?"

Shinichi choked on his coffee. "No!"

"Oh? So what was the special occasion?" Kaito smirked when the detective continued to splutter. "Or did you just miss me that much?"

Shinichi blushed. "You—it wasn't…" He cut himself off when he noticed Kaito's knowing grin. "Okay, fine. I was…thinking about you," he admitted, looking defiantly back at the magician thief.

"Well, I _am_ amazing~. Ow! Why'd you hit me?"

"It's not funny! It—it's just a growing up thing," he muttered, face beet red. "It's not—I mean, it's frustrating, but it's not really a big deal or anything. It—it's just hard to concentrate."

Kaito looked at him for a moment then began to laugh.

Shinichi scowled, blush darkening tenfold. " _I said_ it isn't funny!"

Oh god this was embarrassing. He'd all but admitted to Kaito that he had been spending time fantasizing about the thief—that he'd been dreaming about being pinned down and ravished by Kaito until he couldn't think about anything but his thief.

Downing the rest of his coffee in a quick gulp, he turned back to the counter as he considered whether to pour himself some more. Because of that, he didn't see Kaito get up from the kitchen table until wiry arms wrapped themselves around his waist from behind and a warm body pressed flush against his back. His body responded instantly as though it had a mind of its own, leaning back into the embrace as a delighted shiver ran up his spine.

"There's no need to be embarrassed," a low voice huskily into his ear. "It's only natural. Comes with growing up."

"That's what Haibara said too," Shinichi muttered. "Um, could you…maybe let go now?"

The magician clucked his tongue in mock disapproval. Shifting, he turned Shinichi around so that the detective was now leaning back against the counter and looking up into Kaito's face.

"You know what they say," the thief said with a smirk. "The best way to deal with a problem is to face it head on. You just need to work it out of your system. Don't worry. I'll be right here to help."

Shinichi shuddered. That look in Kaito's eyes was exactly the look he'd pictured in his guilty little fantasies. It was a look that told him he wasn't going to get any sleep tonight. He was going to get exactly what he'd imagined and then some. And it was a good thing he didn't have anywhere to be tomorrow because it was unlikely he'd be able to walk without a limp.

"So," the thief purred, breath ghosting across Shinichi's face. "Shall we get started?"

Shinichi gulped.

Forget walking. He had a feeling he'd be lucky if he could get out of bed tomorrow.

For some reason, the thought didn't bother him one bit. If anything, it just made him feel hotter.

Realizing that resistance was futile, he nodded shyly, blushing madly all the way.

Kaito leaned down to capture Shinichi's lips in a heated kiss. Then he scooped the detective up into his arms and made a beeline for the bedroom.

How could he control himself when Shinichi looked at him like that? He grinned. His Shin-chan was just too cute when he was frustrated and embarrassed. Not that he wasn't always cute, but this was the kind of cute that made Kaito want to pin him down and make him beg for more.

He licked his lips and gave a predatory smirk. His Shin-chan was basically asking to be ravished, and Kaito intended to take full advantage of it. The near future was looking very interesting indeed.

He was more than happy to help fix his detective's _problem_. He already had several plans in mind.

If he'd known all the things running through his thief's mind, Shinichi might have been scared. Fortunately, he couldn't read minds.

* * *

 **-END-**


End file.
